common lcd tv service problems

[spindown]

What are the most common service problems with lcd tv sets?
I'm thinking of getting one and wonder what I may have to deal
with. Thanks Paul

[Bigglez]

What are the most common service problems with lcd tv sets?
I'm thinking of getting one and wonder what I may have to deal
with.

Very similar to problems with modern cars...

[jollyrgr]

Backlights going out is what I see on VGA computer LCDs. This could be the tube itself or the inverter board.

[spindown]

Thanks for the replies. I wonder if there any
books out there that describe how these sets are
constructed and how their problems are diagnosed?
Paul

[Bigglez]

I wonder if there any
books out there that describe how these sets are
constructed and how their problems are diagnosed?

Probably not. Consumer elecronics equipment
usually runs out of features or compatibility long
before anything "wears out". The HDTV LCD TV
sets currently for sale have a backlight life of
about 22 years. Look around your home and see if
any technology currently being used is that old.

With 42inch Philips and Magnavox HDTV sets selling
locally (on ad at Target) for $498 each, who can
afford to be in the TV or appliance repair business?

[Ken1]

Here is one service problem: 2 weeks ago I had an lcd computer monitor come to me for repair. The complaint was that it keeps turning itself off every 5 minutes and needed to be unplugged for several minutes to get it to reset itself. I took it apart and found 3 open or dried out electrolytics in the power supply; 2 in the regulator feedback circuit and the main filter was the third one. After replacing them all, the problem was solved. The monitor is a Samsung made in 2003.

[haklesup]

Very similar to problems with modern cars...

i.e. random unpredictable failure of passive and active components requiring specialty diagnostic equipment to detect and isolate then impossible to find replacement parts available only to dealers. That and worn tires, brakes and windshield chips.

Nice call on the caps ken1. What method did you use to find all of them. O'Scope to look for noise or tedious testing of all suspected passive components? Or was there visual evidence?

[Ken1]

Hi, Thanks for your interest in my troubleshooting method. First of all, the power supply is the only part that is serviceable in the LCD monitor. I have fixed lots of tv's and CRT monitors for people in this community which is so small that everyone knows everyone. The vast majority of failed components in these units are electrolytics, so I always check them out first. About 15 years ago I purchased a Daetron MC300 digital capacitance meter which displays the actual capacitance value of the capacitor. The range of this meter is from 1pf to 1 farad; it's autoranging and it's the same physical size as a pricier dmm. It works great and works in circuit unless there is a low resistance across the capacitor. In this case, the capacitor has to be removed for accurate testing. An ESR meter would eliminate the need to remove the capacitor. As for this particular repair job, I thought the best approach would be to check for any bad electrolytics first so I just tested all the electrolytics in circuit one by one and noting any out of range readings. It takes less than 5 seconds to test each electrolytic. In this case I found a pair of 33uf 50v units that read less than 1uf. The main filter which is a 100uf 400v unit also read less than 1uf. In the secondary of the power supply which is a smps, some electrolytics are in pairs, so the meter reads the sum of the 2 units. I tried out this monitor first before I dug into it and it's interesting to note that unlike CRT displays which always display interference patterns and pulling or bending of the picture whenever the main filter goes, there was no such visual symptoms here; the picture was perfect in every aspect!